It is well-known that so-called fluorochemical surfactants or R.sub.f -surfactants reduce the surface tension of aqueous and non-aqueous solutions to a much greater degree than conventional hydrocarbon surfactants. While surface tensions of aqueous solutions containing hydrocarbon surfactants never go below 22 - 24 dynes/cm, it is possible with R.sub.f -surfactants to achieve surface tensions as low as 15 dynes/cm. It is also well-known that synergistic surface tension effects are achieved from mixtures of different types of R.sub.f -surfactants, as for instance nonionic and anionic R.sub.f -surfactants, alone or in combination with classical hydrocarbon co-surfactants as told by Bernett and Zisman (Reference 1). Tuve et al in U.S. Pat. No. 3,258,423 also disclose the use of aqueous solutions of certain R.sub.f -surfactants or R.sub.f -surfactant mixtures alone or in combination with solvents and other additives as efficient fire fighting agents. Based on the Tuve et al findings many other fire fighting agents containing different R.sub.f -surfactant systems have been disclosed as shown in U.S. Pat. No. 3,315,326 and 3,772,195.
Fire fighting agents containing R.sub.f -surfactants act in two ways:
A. As foams, they are used as primary fire extinguishing agents.
B. As vapor sealants, they prevent the re-ignition of fuels and solvents.
It is this second property which makes fluorochemical fire fighting agents far superior to any other known fire fighting agent.
These R.sub.f -surfactant fire fighting agents are commonly known as AFFF (standing for Aqueous Film Forming Foams). AFFF agents act the way they do because the R.sub.f -surfactants reduce the surface tension of aqueous solutions to such a degree that the solutions will wet and spread upon non-polar and water immiscible solvents even though such solvents are lighter than water; they form a fuel or solvent vapor barrier which will rapidly extinguish flames and prevent re-ignition and reflash. The criterion necessary to attain spontaneous spreading of two immiscible phases has been taught by Harkins et al, J. Am. Chem. 44, 2665 (1922). The measure of the tendency for spontaneous spreading is defined by the spreading coefficient (SC) as follows:
Sc = .gamma.a - .gamma.b - .gamma.i PA1 Sc = spreading coefficient PA1 .gamma.a = surface tension of the lower liquid phase PA1 .gamma.b = surface tension of the upper aqueous phase PA1 .gamma.l = interfacial tension between the aqueous upper phase and lower liquid phase. PA1 A. 0.5 to 25% by weight of amphoteric fluorinated surfactant, PA1 B. 0.1 to 5% by weight of anionic fluorinated surfactant, PA1 C. 0.1 to 25% by weight of ionic non-fluorochemical surfactant PA1 D. 0.1 to 40% by weight of nonionic non-fluorochemical surfactant, PA1 E. 0 to 70% by weight of solvents, and PA1 F. water in the amount to make up the balance of 100%. PA1 R.sup.1 is branched or straight chain alkylene of 1 to 12 carbon atoms, alkylenethioalkylene of 2 to 12 carbon atoms, alkyleneoxyalkylene of 2 to 12 carbon atoms or alkyleneiminoalkylene of 2 to 12 carbon atoms where the nitrogen atom contains as a third substituent, hydrogen or alkyl of 1 to 6 carbon atoms, PA1 y is 1 or zero, PA1 X is oxygen or --NR, wherein R is hydrogen, lower alkyl of 1 to 6 carbon atoms, hydroxy-alkyl of 1 to 6 carbon atoms, or R together with Q forms a piperazine ring, and PA1 Q is a nitrogen containing group selected from PA1 k is 1 or zero, with the provision, that if X is oxygen, k is 1; PA1 R.sup.3 and R.sup.4 are independently of each other hydrogen, alkyl group, substituted alkyl group of 1 to 20 carbon atoms; phenyl group, alkyl or halogen substituted phenyl group of 6 to 20 carbon atoms, polyethoxy or polypropoxy group of 2 to 20 alkoxy units with the proviso that if X is oxygen, R.sup.3 and R.sup.4 are not hydrogen. The alkyl substituents can be alkyl of 1 to 5 carbon atoms, dienyl, hydroxyl, carboxyl, halogen, alkylene dialkylphosphonate such as methylene-diethylphosphonate or a group ##STR3## Phenyl substituents can be methyl, halogen or hydroxyl. Preferably R.sup.3 and R.sup.4 are alkyl groups of 1 to 4 carbons. PA1 --(ch.sub.2).sub.5 -- PA1 --(ch.sub.2).sub.2 -o-(ch.sub.2).sub.2 -- ##STR6## wherein R.sup.2, R.sup.5, A.sup.- and G.sup.- are as defined above, PA1 a + b is an integer from 0-3; and PA1 5a. --(R.sup.2).sub.k -E PA1 5b. --(R.sup.2).sub.k --E.sup.+ -R.sup.--G.sup.- A.sup.- PA1 5c. --(R.sup.2).sub.k -E.sup.+ -G.sup.- PA1 N-[3-(dimethylamino)propyl]-2,(3)-(1,1,2,2-tetrahydroperfluoroalkylthio)suc cinamic acid, PA1 N-methyl-N-(2'-N',N'-dimethylaminoethyl)-2,(3)-(1,1,2,2-tetrahydroperfluoro alkylthio)succinamic acid, PA1 N-(2-dimethylaminoethyl)-2,(3)-(1,1,2,2'-tetrahydroperfluoroalkylthio)succi namic acid, PA1 2-(3)-(1,1,2,2-tetrahydroperfluorodecylthio)succinic acid-mono-[2-(N,N-dimethyl)aminoethyl]ester, PA1 2-(3)-(1,1,2,2-tetrahydroperfluorodecylthio)succinic acid-mono-(2'-quinolino ethyl)ester, PA1 N,n'-bis[(n-propyl-3)-(1,1,2,2-tetrahydroperfluorooctylthio)succinamic monoamido]piperazine, PA1 N-[3-(dimethylamino)propyl]-2,(3)-(heptafluoroisopropoxy-1,1,2,2-tetrahydro perfluoroalkylthio)succinamic acid, PA1 2-(1,1,2,2,-tetrahydroperfluoroctylthio)N-[3-dimethylamine)propyl]-2-methyl succinamic acid. PA1 N-ethyl-N-(2'-N',N' -dimethylaminoethyl)-2,(3)-(1,1,2,2-tetrahydroperfluoroalkylthio)succinami c acid, PA1 N-methyl-N-(2'-N',N' -dimethylaminopropyl)-2,(3)-(1,1,2,2-tetrahydroperfluoroalkylthio)succinam ic acid, PA1 N-[3-(dimethylamino)propyl]-2(3)-(1,1,2,2-tetrahydroperfluorooctylthio)succ inamic acid, PA1 N-[3-(dimethylamino)propyl]-2(3)-(1,1,2,2-tetrahydroperfluorodecylthio)succ inamic acid, and PA1 N-[3-(dimethylamino)propyl]-2(3)-(1,1,2,2-tetrahydroperfluorododecylthio)su ccinamic acid, PA1 Reaction product of N-[3-(dimethylamino)propyl]-] (3)-(1,1,2,2-tetrahydroperfluorodecylthio)succinamic acid and propane sultone PA1 a. they are highly surface active and possess very low interfacial tensions at low concentrations and hence afford films of exceedingly highspreading coefficient; PA1 b. they are amphoteric and thus compatible with all types of fluorosurfactants - anionic, cationic, nonionic, or amphoteric; PA1 c. they are thermally stable at practically useful application and storage temperatures; PA1 d. they are acid and alkali stable; PA1 e. they are biodegradable and non-toxic; PA1 f. they are readily dispersible in water; PA1 g. they are high-foaming and only moderately affected by water hardness; PA1 h. they are inexpensive and commercially available. PA1 ethylene glycol monoalkyl ethers, PA1 diethylene glycol monoalkyl ethers, PA1 propylene glycol monoalkyl ethers, PA1 dipropylene glycol monoalkyl ethers, PA1 triethylene glycol monoalkyl ethers, PA1 1-butoxyethoxy-2-propanol, glycerine, diethyl PA1 carbitol, hexylene glycol, butanol, PA1 t-butanol, isobutanol, ethylene glycol PA1 and other low molecular weight alcohols PA1 such as ethanol or isopropanol wherein PA1 the alkyl groups contain 1-6 carbon atoms. PA1 A. 1.0 to 3.5% by weight of amphoteric fluorinated surfactant, PA1 B. 0.1 to 2.5% by weight of anionic fluorinated surfactant, PA1 C. 0.1 to 4.0% by weight of ionic non-fluorochemical surfactant, PA1 D. 0.1 to 8.0% by weight of a nonionic non-fluorochemical surfactant, PA1 E. 0 to 20% by weight of solvent and water in the amount to make up the balance of 100%. PA1 Corrosion inhibitors (for instance in the case where aqueous AFFF premixes are stored for several years in uncoated aluminum cans). PA1 Chelating agents (if premixes of AFFF agents and very hard water are stored for longer periods of time). PA1 Buffer Systems (if a certain pH level has to be maintained for a long period of time). PA1 Anti-freezes) if AFFF agents are to be stored and used at sub-freezing temperatures). PA1 Polymeric thickening agents (if higher viscosities of AFFF agent -- water premixes are desired because of certain proportioning system requirements), and so on. PA1 A. because of the higher efficiency of the novel R.sub.f -surfactants used and the smaller amounts therefore needed. PA1 B. because of the rather low amounts of solvents required in the new AFFF agents to achieve foam expansion ratios as specified by the military. PA1 Objective: To determine the speed with which an AFFF film spreads across a cyclohexane surface. PA1 Procedure: Fill a 6 cm aluminum dish one-half full with cyclohexane. Fill a 50 .mu.l syringe with a 6% solution of the test solution. Inject 50 .mu.l of the solution as rapidly and carefully as possible down the wall of the dish such that the solution flows gently onto the cyclohexane surface. Cover the dish with an inverted Petri dish. Start the timer at the end of the injection. Observe the film spreading across the surface and stop the timer the moment the film completely covers the surface and record the time. PA1 1. the contribution of each component to the overall performance of the claimed AFFF concentrate, and PA1 2. the superiority of the AFFF concentrate as compared to the prior art.
Where
If the SC is positive, the surfactant solution should spread and film formation should occur. The greater the SC, the greater the spreading tendency. This requires the lowest possible aqueous surface tension and lowest interfacial tension, as is achieved with mixtures of certain R.sub.f -surfactant(s) and classical hydrocarbon surfactant mixtures.
Commercial AFFF agents are primarily used today in so-called 6% and 3% proportioning systems. 6% means that 6 parts of an AFFF agent and 94 parts of water (fresh sea, or brackish water) are mixed or proportioned and applied by conventional foam making equipment wherever needed. Similarly an AFFF agent for 3% proportioning is mixed in such a way that 3 parts of this agent and 97 parts of water are mixed and applied.
Today AFFF agents are used wherever the danger of fuel solvent fires exist and especially where expensive equipment has to be protected. They can be applied in many ways, generally using conventional portable handline foam nozzles, but also by other techniques such as with oscillating turret foam nozzles, subsurface injection equipment (petroleum tank farms), fixed non-aspirating sprinkler systems (chemical process areas, refineries), underwing and overhead hangar deluge systems, inline proportioning systems (induction metering devices), or aerosol type dispensing units as might be used in a home or vehicle. AFFF agents are recommended fire suppressants for Class A or Class B flammable solvent fires, particularly the latter. Properly used alone or in conjunction with dry chemical extinguishing agents (twin-systems) they generate a vapor-blanketing foam with remarkable securing action.
AFFF agents generally have set a new standard in the fighting of fuel fires and surpass by far any performance of the previously used protein foams. However, the performance of today's commercial AFFF agents is not the ultimate as desired by the industry. The very high cost of AFFF agents is limiting a wider use and it is, therefore, mandatory that more efficient AFFF agents which require less fluorochemicals to achieve the same effect are developed. Furthermore, it is essential that secondary properties of presently available AFFF agents be improved. The new AFFF agents should have: (a) a lower degree of toxicity (fish toxicity is a very essential element whenever AFFF agents are dispensed in large quantities and when there is a chance that such agents might pollute receiving streams and lakes; this is a major problem on test grounds where AFFF agents are often used); (b) a lower chemical oxygen demand (COD); good biodegradability (so as not to hinder the activity of microorganisms in biological treatment systems); (c) a less corrosive character so that they can be used in light weight containers made of aluminum rather than heavy, non-corrosive alloys: (d) improved long term storage stability; (e) good compatibility properties with conventional dry chemical extinguishers; (f) an improved vapor sealing characteristic and seal speed, and most importantly; (g) have such a high efficiency that instead of using 3 and 6% proportioning systems it might become possible to use AFFF agents in 1% or lower proportioning systems. This means that 1 part of an AFFF agent can be blended or diluted with 99 parts of water. Such highly efficient concentrates are of importance because storage requirements of AFFF agents will be greatly reduced, or in the case where storage facilities exist, the capacity of available fire protection agent will be greatly increased. AFFF agents for 1% proportioning systems are of great importance therefore wherever storage capacity is limited such as on offshore oil drilling rigs, offshore atomic power stations, city fire trucks and so on. The performance expected from an AFFF agent today is in most countries regulated by the major users such as the military and the most important AFFF specifications are documented in the U.S. Navy Military Specification MIL-F-24385 and its subsequent amendments.
The novel AFFF agents described of this invention are in comparison with today's AFFF agents superior not only with regard to the primary performance characteristics such as control time, extinguishing time and burnback resistance but additionally, because of their very high efficiency offer the possibility of being used in 1% proportioning systems. Furthermore, they offer desirable secondary properties from the standpoint of ecology as well as economy.